Oh, this section is so sad! As a result of the material presented at the conference, Charlie realizes that his gain in intelligence may not last-- that it may be temporary, and he may return to what and who he was before.
Greg

Also, Charlie realized that Drs. Nemur and Strauss, particularly Nemur, was more interested in what he would be able to accomplish--for the benefit of people like Charlie, maybe--as a scientist. Here we also see a good example of situational irony--you the reader has important information that the character does not have, or in Charlie's case, doesn't comprehend at the time. If you recall, Charlie was excited about "being used" by the doctors for this experiment. But he didn't understand Ms. Kinnian's comment when she stated, in short, that people are not always what we think them to be so she understand what was being done by the doctors. Charlie did not understand at the time, hence, the reason why, as we would say today, he had an "ah huh" moment at the conference.